Apparatus for bending rods of corundum and spinel



July 4, 1950 D. M. YENNI ,513,

APPARATUS FOR BENDING RODS OF CORUNDUM AND SPINEL Filed July 25, 1946 2 Shee'ts-Sheet l INVENTOR DONALD M. YENNI BY fl w ATTORNEY July 4, 1950 D. M. YENNl 2, 1

APPARATUS FOR BENDING RODS OF CORUNDUM AND SPINEL Filed July 25, 1946 2 Sheets-Sheet 2 INVENTOR DONALD M. YENNE ATTORNEY Patented July 4, 1950 'UNITED STATES PATENT Y Donald M. Yenni,-Kenmore, N. Y., assig'iior t The LindeAir Products Company, acorporation of Ohio Application July 25, 1946, Serial N0. 686,060

9 Claims. 1

This invention relates to an apparatus for bending a rod of corundum or spinel toform a bend of the desired angular extent and has for an object to provide a simplification in theapparatus for accomplishing this result. Afurther object is to provide a machinecapable of bending such rods with minimum breakage. Another object is to provide such an apparatus which is adapted to provide the desired-results uniformly, quickly and easily, and almost automatically with little skill required of the operator. Yet a further object is to provide means for controlling the pitch of rod convolutions.

In the prior application of McCandless et al., U. S. Patent 2,485,9'7 9, issued October 25, 1949,- are disclosed the broad principles required for bending rods of such materials.

The present invention is an'improvement' upon such prior invention and provides a simple apparatus for'applying those principles to thebending of corundum or spinel rods.

Referring to the drawings:

Fig. 1 is a perspective of oneembodiment of an apparatus according to this invention;

Fig. 2 is a section on the line 2-2 of Fig. 1;

Fig. 3 is a top plan View of a portion of the apparatus of Fig. 1;

Fig. 4 shows therod in position before being bent;

Fig. 5 is the approximate shape of the rod at the conclusion of a 90 bending movement;

Fig. 6 shows-the bending of the rod after a 180 movement;

Fig. 7 shows the completion of 91-270" angular displacement, while Fig. 8 shows the rod after it has been-bent through 360.

Referring to the drawings a substantially straight rod ll! of unicrystalline corundumor spinel is gripped in a chuck supporting one end portion of the rod so that an intermediate part is exposed to a multi-flameburner l2 for heating such intermediate portion to a temperature at which the rod may be bent. The chuck ll is easily removable being formed on the stem of the T. shape shownin Figs. 1 -and'3' ashaving the portion at a right angle to the stem received within an open slot in the end of the block 21 and secured in placeby the two set screwsillustr'ated. The selection of appropriate corundum rods for such-bending is described in the aforem'entioned patent in that corundum-rods having anoptical orientation of 30 to 75 are preferred andstill better those having: suchorientation of 40 to 50 are preferred. Byoptical-orientation is meant" the'angle between the optical axis and the longitudinal axis of the corundum rod. For selectto the longitudinal and optical axes.

ing such rods with such orientation the angular relation of the optical axis with respect to the longitudinal axis of the rod is determined in ways familiar to those skilled in this art and some ap propriate marking is made along one side of the rod to indicate the location of the plane common With the common plane of both such axes generally hori zontal the rod is clamped in the chuck l l prepar atory to its being heated to a temperature suitable for the desired bending. It has-been pointed out in the aforementionedpatent that the plane of bending should be between zero and to the common plane and preferably coincident with the common plane through the optical and longitudinal axes, if breakage of the rods is to be reduced.

Each burner [2 may be for any convenient flame supplying suflicient heat from fuel such as natural gas, acetylene, hydrogen, propane, city gas etc. The particular arrangement of burner ports is not the only one suitable, but is a preferred arrangement found empirically to be satisfactory for maintaining a bending temperature 1 ahove 1500 C. and below the melting point of the corundum or spinel rod being bent during-the course of the bending operation.

Surrounding the burner [2 a radial arm [3 is secured by the set screw [4 to the rotatable pulley l5 and its shaft IS. The pulley I5 is mounted contiguous one side of the stationary bracket 3! opposite the arm I3. The arm l3 has a radial slot I'l cut therein along which the upstanding post l8 may be'adjustabl'y fastened by means of a nut' I9 engaging threads on the post l8 and clamping the headed lower end on the post '25! against the bottom or underside of the slotted arm l3. A lock washer 21 assists in retaining the nut l9 in its adjusted position as is well known in the use of such washers. Rotatably surrounding the post I8 is a bifurcated arm 22 having a sleeve portion surrounding the post I8. The'angularly extending dog 23'is clamped to the bifurcated arm 22-by the nut 24 on the underside of the arm engaging the stem 25 and holding the armor dog 23-clamped in position. The arnr22 and post l8 areradially'adjustable along the rotating arm l3 and dog 23 is'adju'stable along the arm 22. As' shown in Fig. 2 for examplethe-end portion of the dog 23' which cooperates with the rod I0 is provided with a V-shaped notchflli within which the rod I0 is adapted'to be received." To lessen heat'conduction from the rod III to thedog 23 and its supports, the sides 26' of the Vnotch bending. started and the arm I3 rotated orangularly dis-z.

are preferably bevelled to form a knife edge on each side whereby contact with the rod is at two points where the knife edges engage the rod. This V notch assists in angularly moving the free end portion of the rod during the bending operation. The arms I3, 22, and 23 are adjustable to adapt-the machine to different lengths of rods. Only one of these three arms is pivotally connected to the other and that is arm 22 which is pivotally mounted about the upstanding post I8 on the arm I3. By using the three arms illustrated it is possible to have the V notch over or nearly over the flame so that a comparatively short rod mav be bent as desired. q

The chuck II is seen to be slightly downwardly inclined as a result of the adjustment of the block 2! to which the chuck is shown as being fastened in Fig. 3. made adjustable to different degrees of inclination and may be adjusted in various ways such as by means of the pivots 28 supporting the block 21 and the bolt carrying adjustment nuts 29 and 30 below and above the block respectively which hold the block in the desired inclined position of adjustment. The horizontal arm SI of a stationary bracket supports the burner I2 and rotatable arm I3 while a vertical portion 32 of the same bracket pivotally supports the block '21 adjacent an. appropriate stationary wall as illustrated in Fig. 1.

As shown in Figs. 4 to 8 inclusive the burner block has a plurality of ports 33 through which issue fuel gas providing the numerous flames for heating the rod In both before and during the bending operation. with fuel mixture through .a suitable pipe 35 within the inner shaft 34a. For cooling the block against excessive rise in temperature, water or other cooling liquid is supplied through the pipe 35 to the block I2. After passing out of the burner block, the cooling liquid moves through the flexible pipes 35 and 38 to a cooling passage 31 within the horizontal arm 3! of the bracket. Cooling liquid then flows through pipe 39 out of said arm to either a drain or radiator for cooling the'same. As shown in Fig. 1 the flexible connection 40 supplies fuel gas mixture from the mixing pipe 4| to the intake pipe 34 to the block I2.

As shown in Figs. 1, and 2 a belt 42 drives the pulley l from a smaller speed reduction pair of pulleys mounted on a vertical shaft 43 journalled in the stationary frame of the machine as illustrated. A second vertical shaft 44 drives the shaft through the speed reduction pulley and belt drive from a motor it through speed reducing mechanism 45. A rheostat 4? controls the speed of rotation of the movable arm I3 to a slow speed of about R. P. M. or less. The snap switch 48 controls the circuit of the motor 46 enabling the drive motor and the rotating arm I3 to be stopped at any desired position in its travel so that the bend in the rod may be of any desired angular extent.

After clamping the unicrystalline rod If] in the chuck with the plane of its optical and 10hgitudinal axes substantially horizontal and inclined to the plane of the rotating arm l3 at a small acute angle as illustrated, the flames from the burner block are started and the intermedi-.

ate portion of the rod over these flames is heated to between 1500 C. and the melting point at which temperature the rod is in condition for At such temperature the motor is The block I2 issupplied placed in the counter clockwise direction illus trated in Figs. 4 to 8 inclusive. From these figures it will be apparent that the radius of curvature in the bent rod is determined by the length of the heated portion and also by the angular extent of the bending movement imparted to the red. It first is shown in" Fig. 5 :where the radius of curvatureis large, but diminishes as the bending of the rod progresses. Due to the V notch 26 being moved in a substantially horizontal plane and dueto the slight inclination of the rod l0 and chuck II as shown in Figs. 1 and 2, the cool outer end portion of the rod is free to pass under the clamped end of the rod and chuck without interference. The rod having a 360 bend shown in Fig. 8 is one type found proper for use as a thread guide in the textile machinery This block may be art while bends of greater or less extent may possess other uses.

Among the advantages of this invention may be mentioned the freedom from necessity of using a die or form in determining radius since the radius of curvature is dependent on the heated length and on the angular extent of the bending movement. Changes in either affect the radius of bending. The speed of operation is slow enough to permit the apparatus to be stopped at any desired angular position of travel to control the extent of the bending movement. The heating of the rod simultaneously when it is being bent insures uniformity in distribution of the heating and any flexural stresses set up in the material during such bending.

, The product of the present method and apparatus may be highly flame polished if the rod has been heated hot enough to cause superficial melting, and is possessed of great hardness and smoothness adapting it for many uses. The'adjustment in the height of the chuck H and in its angle of inclination to the plane of rotation of the arm I3 may control the pitch or spacing of the convolutions formed in the bend. The crossed or overlapped portions of the bent rod are either contiguous one another, or separated. The apparatus assists in providing uniformity in the bends. I I

The flame head consumes approximately 15 cubic feet per hour of oxygen and a smaller quantity of natural gas during pigtail formation. The bending cycle for rods upto inch in diameter requires about 30 seconds for preheating the rod and about 10 seconds for bending the rod. Rods of larger diameter will require more time for the bending operation and-will need more heat and a longer preheat period.

Bending of a corundum rod differs from the bending of an ordinary glass rod, for example, in numerous respects among which may be mentioned: (a) the need for having the plane of the longitudinal and optical axes bearing a prescribed angular relation to the plane of bending. Glass may be bent in any direction with equal facility. (1)) Corundum has a sharp melting point (that is, the viscosity-temperature curve shows a discontinuity of tremendous proportions) and therefore has a narrow useful plastic range. Glass on the other hand has a wide plastic range in the sense that its viscosity decreases along a fairly smooth curve as the temperature rises. (c) A mean temperature for bending corundum is higher than a mean temperature for glass bending. (d) C'orundum and spinel are unicrystalline whereas glass and other amorphous materials are considered liquids under any temperature conditions according to many authorities.

I claim:

1. An apparatus for bending a rod of corundum or the like comprising stationary gripping means for an end of the rod, means for heating an intermediate portion of the rod to above a white heat, and means for engaging the end of the rod opposite said gripping means to bend the same, said last end engaging means including a rotatable arm, driving means for said arm, a post radially adjustable along said arm, a second arm pivotally secured to said post, and a dog adjustable along said second arm and provided with a Vshaped notch engaging said rod for angularly displacing one end of the rod with respect to the other about the heated portion, said V-shaped notch having the sides thereof sharpened as knife edges for point contacts with said rod to reduce heat transfer from the rod to the dog.

2. Apparatus for bending a rod of corundum or spinel comprising means for clamping one end portion of the rod and supporting the rod, a multi-flame block for heating an intermediate portion of the rod to a bending temperature, and a rotatable means having movement around said block for engaging the free end portion of the rod in bending it about its heated intermediate portion, the portion of said last mentioned means engaging the rod being shaped to reduce heat conduction from the rod, said last means including an arm pivotally secured to a rotatable carrier and dog projecting inwardly from said arm and clamped thereto, said dog engaging said rod at its inward end.

3. Apparatus for bending a rod of corundum or spinel comprising clamping means for supporting an end portion of the rod, a heater for a portion of the rod being bent, a tubular outer rotatable shaft surrounding an inner tubular shaft through which energy is supplied for said heater, and an arm projecting from said outer shaft for engagement with said rod at its end portion remote from said clamping means, said heater cooperating with a, portion of the rod intermediate said arm and clamping means.

4. Apparatus for bending a rod of corundum or spinel comprising clamping means for supporting an end portion of the rod, a stationary heater for the portion of the rod being bent, a support for said heater, a shaft rotatable around said heater support, and an arm extending from said shaft and movable around said heater for bending said rod in its heated portion intermediate said clamping means and said arm.

5. Apparatus according to claim 4 in which said heater is of area to continue during the bending operation the heating of the portion of the rod being bent.

6. Apparatus for bending a rod of corundum or the like comprising stationary gripping means for an end of the rod, means for heating an intermediate portion of the rod to a bending temperature, and means for engaging the end portion of the rod opposite said gripping means to bend the same, said last end engaging means including a rotatable arm, driving means for said arm, a post projecting from said arm, a second arm pivotally secured to said post, a dog clamped to said second arm and engaging said rod for angularly displacing one end of the rod with respect to the other about said heated portion.

'7. Apparatus for bending a rod of material like corundum or spinel having a sharp melting temperature and requiring heating during bending, said apparatus comprising in combination a burner block from which a pluralityof flames is adapted to issue in the same general direction, a bending force applicator rotatable around said flames for at least 360 in bending a rod while the same is being heated, means for clamping an end portion of the rod to be bent with its longitudinal axis forming an acute angle with a plane of movement of said bending force applicator, means for supporting said bending force applicator adjacent said burner block, driving means for said bending force applicator, and fuel supply means for said flames leading to said burner block from a direction to be out of the path of movement of said bending force applicator and its driving means as well as said rod.

3. Apparatus for bending a rod of corundum or spinel comprising in combination a burner having a plurality of upwardly directed openings, means above and to one side of said burner for clamping an end portion of the rod to be bent with an opposite end portion of the rod free and an intermediate portion of the rod heated to its bending temperature by flames from said burner openings, a bending force applicator rotatable around said burner, fuel supply means to said burner, and a support for said bending force applicator below the upper end of said burner and through the axis of which said fuel supply means extends, said bending force applicator engaging the free end portion of the rod beyond said heated intermediate portion and being of a height to pass under the clamped end of said rod.

9. An apparatus for bending a rod of material having a sharp melting point and requiring heating of the rod during bending, said apparatus comprising clamping means for clamping one end portion of said rod leaving the other end portion free, and a burner having a plurality of openings for heating an intermediate portion of said rod, said burner being located on one side of said rod clamping means, fuel supply means leading to said burner and located to one side of and spaced from said rod clamping means, and a bending force applicator rotatably supported adjacent the free end portion of the rod, there being suficient clearance around said applicator to enable the same to rotate through an angle of at least 360 while the rod is being heated and bent in a plane at a small acute angle to the clamped end of said rod and away from said fuel supply means, whereby said bending force applicator during its rotation will be free from any contact with either the clamped end of said rod or said fuel supply means.

DONALD M. YENNI.

REFEEENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,265,070 Goode Dec. 2, 1941 2,286,893 Boisson June 16, 1942 2,296,321 Wellech Sept. 22, 1942 2,242,609 Ellefson Feb. 22, 1944; 

